diff --git a/lib/Misc/Query.php b/lib/Misc/Query.php
index 941ea78..b190288 100644
--- a/lib/Misc/Query.php
+++ b/lib/Misc/Query.php
@@ -6,16 +6,10 @@
 declare(strict_types=1);
 namespace JKingWeb\Arsse\Misc;
 
-class Query {
+class Query extends QueryFilter {
     protected $qBody = ""; // main query body
     protected $tBody = []; // main query parameter types
     protected $vBody = []; // main query parameter values
-    protected $qWhere = []; // WHERE clause components
-    protected $tWhere = []; // WHERE clause type bindings
-    protected $vWhere = []; // WHERE clause binding values
-    protected $qWhereNot = []; // WHERE NOT clause components
-    protected $tWhereNot = []; // WHERE NOT clause type bindings
-    protected $vWhereNot = []; // WHERE NOT clause binding values
     protected $group = []; // GROUP BY clause components
     protected $order = []; // ORDER BY clause components
     protected $limit = 0;
@@ -34,24 +28,6 @@ class Query {
         return $this;
     }
 
-    public function setWhere(string $where, $types = null, $values = null): self {
-        $this->qWhere[] = $where;
-        if (!is_null($types)) {
-            $this->tWhere[] = $types;
-            $this->vWhere[] = $values;
-        }
-        return $this;
-    }
-
-    public function setWhereNot(string $where, $types = null, $values = null): self {
-        $this->qWhereNot[] = $where;
-        if (!is_null($types)) {
-            $this->tWhereNot[] = $types;
-            $this->vWhereNot[] = $values;
-        }
-        return $this;
-    }
-
     public function setGroup(string ...$column): self {
         foreach ($column as $col) {
             $this->group[] = $col;
@@ -81,11 +57,11 @@ class Query {
     }
 
     public function getTypes(): array {
-        return ValueInfo::flatten([$this->tBody, $this->tWhere, $this->tWhereNot]);
+        return ValueInfo::flatten([$this->tBody, $this->getWhereTypes()]);
     }
 
     public function getValues(): array {
-        return ValueInfo::flatten([$this->vBody, $this->vWhere, $this->vWhereNot]);
+        return ValueInfo::flatten([$this->vBody, $this->getWhereValues()]);
     }
 
     protected function buildQueryBody(): string {
@@ -94,11 +70,7 @@ class Query {
         $out .= $this->qBody;
         // add any WHERE terms
         if (sizeof($this->qWhere) || sizeof($this->qWhereNot)) {
-            $where = implode(" AND ", $this->qWhere);
-            $whereNot = implode(" OR ", $this->qWhereNot);
-            $whereNot = strlen($whereNot) ? "NOT ($whereNot)" : "";
-            $where = implode(" AND ", array_filter([$where, $whereNot]));
-            $out .= " WHERE $where";
+            $out .= " WHERE ".$this->buildWhereBody();
         }
         // add any GROUP BY terms
         if (sizeof($this->group)) {
diff --git a/lib/Misc/QueryFilter.php b/lib/Misc/QueryFilter.php
new file mode 100644
index 0000000..12c3bd3
--- /dev/null
+++ b/lib/Misc/QueryFilter.php
@@ -0,0 +1,71 @@
+<?php
+/** @license MIT
+ * Copyright 2017 J. King, Dustin Wilson et al.
+ * See LICENSE and AUTHORS files for details */
+
+declare(strict_types=1);
+namespace JKingWeb\Arsse\Misc;
+
+class QueryFilter {
+    protected $qWhere = []; // WHERE clause components
+    protected $tWhere = []; // WHERE clause type bindings
+    protected $vWhere = []; // WHERE clause binding values
+    protected $qWhereNot = []; // WHERE NOT clause components
+    protected $tWhereNot = []; // WHERE NOT clause type bindings
+    protected $vWhereNot = []; // WHERE NOT clause binding values
+
+    public $filterRestrictive = true;
+
+    public function setWhere(string $where, $types = null, $values = null): self {
+        $this->qWhere[] = $where;
+        if (!is_null($types)) {
+            $this->tWhere[] = $types ?? [];
+            $this->vWhere[] = $values;
+        }
+        return $this;
+    }
+
+    public function setWhereNot(string $where, $types = null, $values = null): self {
+        $this->qWhereNot[] = $where;
+        if (!is_null($types)) {
+            $this->tWhereNot[] = $types;
+            $this->vWhereNot[] = $values;
+        }
+        return $this;
+    }
+
+    public function setFilter(self $filter): self {
+        $this->qWhere[] = "(".$filter->buildWhereBody().")";
+        $this->tWhere[] = $filter->getWhereTypes();
+        $this->vWhere[] = $filter->getWhereValues();
+        return $this;
+    }
+
+    protected function getWhereTypes(): array {
+        return ValueInfo::flatten([$this->tWhere, $this->tWhereNot]);
+    }
+
+    protected function getWhereValues(): array {
+        return ValueInfo::flatten([$this->vWhere, $this->vWhereNot]);
+    }
+
+    public function getTypes(): array {
+        return $this->getWhereTypes();
+    }
+
+    public function getValues(): array {
+        return $this->getWhereValues();
+    }
+
+    protected function buildWhereBody(): string {
+        $glue = $this->filterRestrictive ? " AND " : " OR ";
+        $where = implode($glue, $this->qWhere);
+        $whereNot = implode(" OR ", $this->qWhereNot);
+        $whereNot = strlen($whereNot) ? "NOT ($whereNot)" : "";
+        return implode($glue, array_filter([$where, $whereNot]));
+    }
+
+    public function __toString() {
+        return $this->buildWhereBody();
+    }
+}